Method of quenching metals



Wm! 13,, K9 M. GORDON METHOD OF QUENCHING METALS Filed July 6, 1954, 2 Sheets-Sheet 1 INVENTOR.

Mann 6mm am United States Patent METHOD OF QUENCHING METALS Mack Gordon, Cleveland, Ohio Application July 6, 1954, Serial No. 441,482

9 Claims. (Cl. 148-131) This invention relates to improvements in a heat exchange medium and in a method for the control of crystalline structures in compositions of metals and metalloids which have a crystal structure transformation range, and involving the heating of a composition to a temperature above the transformation range follows by cooling in my improved medium through the transformation range resulting in a desired crystal structure.

One of the objects of the present invention is to provide a heat exchange medium which is almost infinitely variable so that the medium may be tailored to fit various specific problems.

Another object of the present invention is to provide a metal treating liquid whereby the quenching action is not as harsh as that of water, and in which the quenching action of oil may be substantially matched, or the action varied between water and oil, or made slower than the action of oil, all without the fire and skin irritating hazards found in the use of oil.

Another object of the present invention is to provide a heat exchange medium utilizing various gums in water solution. The heat exchange characteristic of the medium may be changed by varing the amount of gum in the water solution from a percentage very close to zero up to about 1.0 to 1.25 percent. Above this range with most gum, no particular advantage seems to be achieved and a coating of gum sticks to the bar when it is quenched so that the gum is removed from the bath and the bar has to be cleaned.

Another object of the present invention is to provide a combination of a water solution of a gum together with a wetting agent which substantially varies the heat exchange characteristics of the medium.

Other objects and advantages of this invention will be apparent from the drawings and description and the essential features thereof will be set forth in the appended claims.

In the drawings,

Fig. 1 shows the cooling curves for several different quenching media; while Fig. 2 shows the use of the present invention in fitting the quenching medium to a particular type of steel.

While my invention is applicable to various heat exchange problems in the treating of metals, I shall first explain the application thereof to the quenching of metals, particularly carbon-containing ferrous materials such as steel, and thereafter refer to certain other uses of the invention.

Throughout the following discussion relating to steel, the zone of 500 degrees Fahrenheit is used as a measure of the various quenching media because this is approximately the temperature at which martensite starts to form in many heat treating grades of steel. It is desirable to cool the steel to this approximate temperature before it has an opportunity to transform at higher temperatures from austenite to pearlite. Alloying elements are used in certain grades of steel to retard this transformation at the higher temperatures. Many grades of steel when quenched in water show a tendency to crack and distort because of the sudden and harsh action of the water on the metal. When components of an appropriate alloy steel are quenched in oil, hardening will be achieved with cooling rates considerably slower than that obtained with water and with less tendency for cracking and distortion. The present invention teaches the achievement of cooling rates between those of water and oil and also the achievement of rates slower than that attained with oil commonly in use, where such slower cooling is necessary to achieve the metal structure desired.

Various gums soluble in Water have been found useful for my purpose. One of these gums is carboxy methyl cellulose which is made available in several standard grades by the Hercules Powder Company. This gum, sometimes hereinafter referred to as CMC is the sodium salt of carboxy methyl cellulose having a closely controlled number of sodium carboxy methyl groups introduced into the cellulose molecule to bring about solubility in water. The cellulose is first treated with alkali and then is reacted with sodium monochloroacetate. Since each anhydroglucose unit in the cellulose structure contains three reactive hydroxyl groups with which the sodium monochloroacetate can react, theoretically complete reaction would mean the introduction of three sodium carboxy methyl groups per anhydroglucose unit. Such a completely reacted product would be said to have a substitution of 3.0. However, the optimum combination of physical properties for this gum is actually achieved with a substitution of from 0.3 to 1.2 (0.7 being the regular type). This regular purified type is designated as Hercules CMC70 and the 1.2 substitution is designated as Hercules CMC-120. These gums are made in several viscosity types, that designated as high being of a higher molecular weight and, therefore, of a higher viscosity. The polymer in such a case might have as many as 1000 glucose units in the chain. That designated as low is of lower molecular weight and, therefore, of a lower viscosity in which the polymer might have as low as 50 glucose units in the chain.

In Fig. 1, the cooling curve for water is indicated at A. The cooling curve for a standard commercial quenching oil, Houghton No. 2., is indicated at B. The other three curves of Fig. l are for mixtures of CMC-120 high in water together with 0.1 percent Tergitol NPX which is an alltyl phenyl polyethylene glycol, this latter being a non-foaming wetting agent comprising a higher sodium alkyl sulfate and sold by Union Carbide & Carbon Company. The purpose of this wetting agent will be explained later. Curve C is 0.3 percent CMC-120 high in water plus Tergitol. Curve D is 0.5 percent CMC-120 high in water plus Tergitol while curve E is 0.75 percent CMC-120 high plus Tergitol. l t will be noted that the Curve C lies between curve A for water and curve B for oil. Curve D approximates very closely curve B. Curve B shows a slower cooling rate than that: for the commonly used quenching oil of curve B.

The tests from which these curves of Fig. 1 were plotted were performed in a quenching solution at a temperature between and 82 degrees F, the solution being in a closed system including a four inch pipe several feet high surrounded by a reservoir. The top of the pipe was above the reservoir and the quenching solution was pumped upwardly through the pipe passed over the top and back into the reservoir. These particular tests used turbulent agitation which was achieved with a propeller type stirrer in the bottom of the pipe. The quenching sample was a one inch diameter bar of Vega steel about three or four inches long. This steel contains 0.70 percent C, 2.00 percent Mn, 0.30 percent Si,

1.00 percent Cr, 1.35 percent Mo, and the balance iron. The temperatures were obtained from a Speedomax chart record of the cooling temperatures 'rom thcrocouples embedded inch below the surface of the bar.

The results so far described and shown in Fig. 1 and Tables I and II were determined in an agitated bath and a cooling of the steel sample from 1550 degrees Fahrenheit initial temperature. The next results listed utilize It was discovered that the quenching action at higher the same equipment but without the propeller type stirrer temperatures was held up because of steam bubbles forming on the surface of the bar and' this was broken down Table H both by the turbulent agitation of the quenching medium and also further by the use of a wetting agent. The data Quenchant 1 2 3 for th1s ser1es of tests 15 shown 1n Table I. The data m the column 2 of thls table, showing the temperature Sam 03% CMC70 Low 001% gym which the coohng rate became less than 100 degrees 1*. thctiesAFlOO 5 a o-1,080 0-20 per second, shows the temperature at which the cooling gf 70 Low, 001 7 82M 220 M4 rate rather abruptly changes from the initial rapid quench- Soln. 0.5% CMC70 7 7 J thcties AFIOO 700-12 0 "-28 mg rate. The data 1n column 3 of th1s Table l, cone S01; 05% CMC70 LOW, 031% spondlng to the quenchmg tlme requ1rcd for the thermotneties AFl00. 7 ago-1,200 4-10 couple to reach 500 degrees F is regarded as an impor OEQZ; ZY Z'E6iZ Z 'E h: 9 1045K tant cr1ter1on of the quenchlng characterisucs because tlhctilcsu 12 oco-1,1001. '12-24L 500 degrees Fahrenheit 1s near the temperature at WhlCll 211m 12 1y30O 1,420L 27ml,

0 1.0 Table l S thhjetics 1 100 12 1, 310-13001. 21-271.

. 1.0 thetics XF100 11 1, zoo-1,340 24-30 Quenchant 1'I 2 3* l*-Viscosity centi oises. Oil (Houghton N0. 2) 1, 020-1,370 21-43 25 2*-1cmperature a t which coloing rate became less than 100 deg. per Soln. 0.2% OMC120 High, 0.1% Tergitol sec.,

NPX 7 8501,030L 13L 3*Quenehing time required for thermocouple to reach 500 degrees F., 8.011103% OMO120High,0.1% Tergitol 11 6 1 330 10 r seconds.

00-, S0111. 0.1% 01130120 ll'igh,0.1% Tergitol 3 Table III 17 1,000-1, 200 27-30 S0ln.0.5% OMG120 High" 23 1, 010-1, 300 15-20 Soln.0.5% CMClZO Hi 11,0. 26 940-1, 270 10-38 30 Soln. 0.75% OMC120 High. 50 820-1, 280 21-38 Quenching Soln. 0.15% CMO120 High, Time Re- 54 l,170l,320 32-48 Addition quired for S0111-J0-3% OM070 LOW, TeTgltOl l0 1 080 1 280 19 39 Quenchant Percent 'llhegnoegtgal:

"o eae Soln. 0.47 CMC70 Low, 0.17 Ter itol D g' NPX? 13 1, 020-1, 070 20-30 35 lahloliiign 80111. 0.5% CMC70 Low, 0.1% Tergitol NPX 15 1, 150-1, 280 18-34 S0111. 0.0% CMC70 Low, 0.1% 'lergitol 0.1 11. 5 2a 1, 0804.240 20-47 0.2 15.3 Soln. 0.75% CMC70 Low 0.1% Tergitol S0111, CMO120 High 0. 3 18.2 29 1,210-1, 370 37-42 0.5 40.0 Soln. 1.0% CMC70 Low 49 1, 200-1, 310 34-47 40 0. 75 73.0

1*Visc0sity ccntipoises. 2*Femperature at which cooling rate became less than 100 deg. per i h f i h i I other Words th pump moved 500.,

3*-Quer1ching time required [or thermocouple to reach 500 degrees [116 quenchant up the fOUI Inch plpe In what I have Second} I termed laminar fiow past the sample being quenched and martensite starts to form in many heat treating grades thus out the top of the pipe and back to the reservoir of steel. A range of values 1s given in columns 2 and 3 and pump. Otherw1se, these tests are hke those previousof Table No. 1. Because counterclockwlse c rculat on ly reported. of the quenchmg solution occurred In the four 1nch pipe Table III shows that solutions of CMCIZO h1gh varydue to the propeller type stirrer, the tests were run with ing from 0.1 percent to 0.75 percent of the gum in a the thermocouple in different locations with respect to water solution increased the quenching time required for the flow of quenchant. When the letter L follows the the thermocouple to reach 500 degrees F. from 11.5 seedata, they were obtained with the thermocouple in the onds to 73 seconds. leading or upstream position only. Otherwise, the data Table IV shows a similar set of tests in the laminar show the range obtained with the thermocouple in the bath described in connection with Table 111 but using leading or upstream position, then at 90 degrees to this various solutions of CMC70 low in water and without position, and then with the thermocouple in the downany wetting agent. This table shows that increasing the stream position 90 degrees further, or 180 degrees from percent of CMC in the solution from 0.1 percent to 0.75 the first position. Therefore, the data of Table I reppercent increases the time required for the quenched resent the range of cooling curves that would be obtained piece to reach 500 degrees F., the time increasing gradaround the one inch diameter bar quenched in solutions ually from 7.5 seconds to 50 seconds. agitated in a similar manner. f i 1 b Anothc; gulmgvhich i; ulseful in my invention is car- In Table II, I show another series 0 tests uti izing so uoxy met yl y roxy et y cellu ose. T. e products of tions of CMC70 low in water with small percentages of which tests are shown in Table V are sold by Hercules Synthetics AF 100 which is a polyethyl glycol ether of Powder Company under two designations. CMHEQ37 alkylated phenol a commercial wetting agent of non- 1nd1cates a 0.3 substltutmn of the carboxy methyl radical foaming character made and sold by Hercules Powder and 0.7 substitutlon of the hydroxy ethyl rad1cal. Company. These tests in Table No. II show in the first CMHEC-4 3 designates 0.4 substttuuon of the carboxy six tests that increasing the percent of gum from 0.3 pedrmelthyl radical and sgllbshltuuon of the nydroxhy ethyl cent to 1.0 percent gradually increased the v1scos1ty an ra ica e tests 0 a e were 112M311 under t e same on the average, increased the time necessary for the coolcircumstances as Table III and show that whereas a ing curve to reach 500 degrees F. The last four tests 0.1 percent solution of CMHEC43 and water takes 2 listed in Table II show that after a 1 percent solut on seconds for the quenched bar to cool to 500 degrees F., of CMC70 low was reached, a variation of the wettmg I a solut1on of 0.2 percent of the same gum takes 11 agent from .01 percent to .10 percent made very little seconds to cool to the same temperature. Of the solutions of CMHEC37, 0.1% solution in water took 3.5

change in the quenching curve.

seconds to cool to 500 degrees F. whereas 0.15 solution took 8.5 seconds and 0.2 solution took 11.5 seconds.

Table IV Quenehant 1 2* 3* 7. 5 13 Soln. CMC70 Low 14 30 50 Table V Quenchant I 1* 2' 3* 0.1 380 2 OMHEOB i0. 2 1, 000+ 11 0.1 530 3. 5 CMI-1EC37 0.15 750 8. 5 0. 2 1, 020 11. 5

Table VI Quenchant 1 2* 3* 0.1 800 28 Methyl Cellulose (L2 820 40 Table VII Quenehant I 1* I 2 i 3* 0.1 440 7 I-Iydroxyethyl Cellulose (\VPHS) 0. 2 1,080 10. 5

*Addition percent.

2*Temperature at which cooling rate became less than 100 degrees per second Fahrenheit.

3*dQuenching time required thermocouple to reach 500 degrees F., sccon s.

Another gum useful in carrying out my invention is methyl cellulose although I do not believe it is quite as satisfactory as others which I have mentioned above. Table VI run under the same conditions as the test of Table III shows that for a 0.1 percent solution of methyl cellulose in water the time for the quenching piece to cool to 500 degrees Fahrenheit is 28 seconds whereas a 0.2 solution of the same required 40 seconds. .One of the disadvantages of methyl cellulose is that some of it seems to cling to the bar as it leaves the quenching bath.

Still another gum useful in the carrying out of my invention is hydroxy ethyl cellulose. That used in carrying out the tests in Table VII is a commercial product sold by Union Carbide & Carbon Company under the designation WPHS. This hydroxy ethyl cellulose must be substituted at least 1.2 to obtain water solubility. The above grade WPHS is a 2.0 substituted hydroxy ethyl radical in the cellulose solution. The tests of Table VII, run under the same conditions as the tests of Table III, show a gradual increase in the time necessary for the quench piece to cool to 500 degrees Fahrenheit as the solution is increased from 0.1 percent WPHS to 0.3 percent of the same solution.

Table IX Quenchant 1* 2* 3* 0.5% CMC120 Med., 0.10% Duponol ME 900 14 1.0% OMO120 Med., 0.02% Duponol ME 900 46 (700 F.)

1*Addition percent.

2*-Temperature at which cooling rate became less than degrees per second Fahrenheit.

3*dQu0nching time required thermocouple to reach 500 degrees F., sccon s.

A*Soluti0n temperature, degrees Fahrenheit.

B*-Temperature at which cooling rate became less than 100 degrees per second, Fahrenheit.

O*dQ,uenchiug time for thermocouple to reach 500 degrees Fahrenheit,. secon s.

Table VIII shows tests under the same conditions as Table III using the hydroxy ethyl cellulose mentioned above in connection with Table VII. Table VIII shows somewhat higher concentrations of the HEC plus the wetting agent Tergitol 08 which is another non-foaming sodium octyl sulfate wetting agent containing 38 percent solution in water and made and sold by Union Carbide & Carbon Company. Table VIII shows that increasing the HEC from 0.5 percent to 1.0 percent HEC in a water solution plus 0.1 percent Tergitol 08 changes the quenching time required to reach 500 degrees Fahrenheit from 1.5 seconds to 21 seconds.

Table IX shows two tests run under the same conditions as Table III but using a carboxy methyl cellulose medium with very slight additions of a wetting agent Duponal ME which is a foaming type of wetting agent marketed by du Pont. Duponol ME is a sodium salt of lauryl alcohol sulphate containing a minimum of electrolyte. This foaming type of wetting agent makes a collection of small bubbles on the surface of the bar in the quenchant and, therefore, slows down the quenching curve. This test shows that increasing the solution from 0.5 percent CMC 120 medium plus 0.1 Duponal to 1.0 percent CMC 120 medium plus 0.02 percent Duponal changes the quenching time required for the thermocouple to reach 500 degrees Fahrenheit from 14 seconds to considerably over 46 seconds since the piece reached only 700 degrees Fahrenheit after 46 seconds and the test had to be stopped for other reasons.

The concentration of the gum in the quenching solution is not the only factor which governs the cooling rate. The temperature of the solution is a factor also. Referring to Table X several tests are shown made under the conditions of Tables I and II and utilizing two different concentrations of CMC-120 high. In the first three tests the solution was 0.25 percent CMC in a water solution and the time necessary to cool the steel bar to 500 degrees Fahrenheit varied from 2 seconds when the quenchant solution was at 81 degrees Fahrenheit to 39 seconds when the solution temperature was degrees Fahrenheit. The next three tests recorded in Table X utilize a solution of 0.50 percent CMC-120 high in a water solution and indicate that at 82 degrees Fahrenheit solution temperature the time necessary to cool the piece from 1550 degrees Fahrenheit to 500 degrees Fahrenheit was 11 seconds whereas at a qucnchant temperature of 164 degrees Farhenheit the time required to cool the piece to the same temperature was 60 seconds. Thus, it appears that the temperature of the quenching solution will have an effect-on the heat exchange rate, as would be expected.

Fig. 2 illustrates the use of my invention in working out a quenching method for a given steel. Curve B is the cooling curve for oil as in Fig. 1 and curve C is the cooling curve utilizing a 0.3 percent solution of CMC 120 high plus 0.1 percent Tergitol NPX as previously explained. The curve F of Fig. 2 is an isothermal transformation curve for SAE 4140 steel. Those familiar with the practice of metallurgy will understand that when the left bar of steel is heated to 1500 or 1550 degrees F., the composition becomes austenite which is unstable. Above and to the left of curve F of Fig. 2 represents this austenitic structure. If thepiece is quenched in oil, then, where the cooling curve B crosses the curve F at the point g1 transformation to pearlite commences and this will continue until the cooling curve B crosses the line Ms as the point g2 where the balance of the structure will crystalize as martcnsite. It should be understood that the Ms curve is here shown at approximately 660 degrees P. which is the zone where the martensitic structure commences in this type of steel. On the other hand, if a harder structure is desired, than that desired by quenching in oil, a solution may be made up according to the teachings of my invention utilizing 0.3 percent CMC120 high in water plus 0.1 percent Tergitol NPX and the piece may be quenched in this solution. Referring to Fig. 2, it will be noted that at the point hl where curve C crosses the line Ms, the structure of the piece is still autenitic and is Well to the left of the point I12 where curve'F intersects the line Ms. Thus, the maximum amount of martensite will be formed from the austenite utilizing the teachings of my invention. Of course, a inartensitic structure could be arrived at utilizing water as the quenching medium but this often results in cracks and distortion of the piece of steel.

By utilizing my invention, the desired structure in the steel may be provided without the harsh treatment of water and without the formation of pearlite which would follow the use of the quenching oil illustrated in curve B. Obviously, if a greater percentage of pearlite was desired than is found utilizing the oil as a quenching medium illustrated by curve B in Fig. 2, then one might use my quenching solution illustrated by the cooling curve E of Fig. l and obtain a still higher percentage of pearlite than is possible utilizing oil. Thus, utilizing the various quenching baths set forth in the various tables of my specification, one may tailor a quenching bath to suit any desired steel and any desirable structure in quenching that steel from austenite.

Other uses of my invention will occur to those familiar with heat exchange mediums. It has already been used in induction hardening where a very thin external layer of a piece of metal is heated to the transformation point by high frequency currents after which the piece is cooled in a. spray. Utilizing the teachings of my invention, this spray may haveany desired characteristic.

We are also successfuliy treating pearlitic malleable iron having approximately 2.5% carbon by heating to 14001600 F., then quenching it in a solution of 0.5% CMC 120 high, and then cooling it in the solution mentioned until the metal cools below the critical point.

A spherical ball of steel quenched in water showed a surface stress of 130,000 pounds per square inch. A ball of identical shape and material quenched in a water solution containing 0.5% CMC 17.0 high, as taught herein, showed a surface stress of 90,000 pounds per square inch.

All solutions mentioned in this specification give the percent of solids in solution by weight.

It will thus be seen that when solutions of these variousrgums were used in quenching finch diameter bars with a quenchant velocity of 100 feet per minute, certain solutions of each gum cooled the bars at rates :8 intermediate between the cooling rates produced by water and oil. More concentrated solutions of some of the gums developed cooling rates slower than oil.

Solutions of 0.5 percent CIVIC- high in water with 0.1 percent Tergitol NPX wetting agent, or 0.4 percent CMC,70 low with 0.,1 percent Tergitol NPX Wetting agent, produced cooling curves that were very closely within the range of curves for oil commonly used for quenching.

The steel bars mentioned above, when quenched in baths containing more than 1.0 to 1.25% of the soluble gum, were coated with gum .as they came out of the bath. This is usually undesirable.

Solutions wherein the concentration of gum in the water was in the range from 0.1 percent to 1.0 percent or slightly higher would appear to furnish the necessary range of quenching solutions for steel.

Increasing the concentration of the gum in the water solution increases the quenching time to 500 degrees Fahrenheit and decreasing the gum concentration in the solution decreases the same quenching time.

Under a given set of conditions and with a constant concentration of gum in the water solution, an increase or decrease in the cooling rate for quenching may be arrived at 'by varying the temperature of the solution.

All of the gum additions gave slower cooling curves than Water and, therefore, any'of them might be useful additions to water where a water quench is too quick and harsh.

Wetting agents in small percentages may be added to the gum solution with a generally favorable effect especially in the use of non-foaming wetting agents.

The cooling rate for certain gum solutions may be decreased by the addition of a foaming wetting agent, which forms a blanket of bubbles on the quenched piece.

The term gum as used in my specification and claims refers to synthetic gums not found in nature and exemplified by the specific water soluble materials named herein as the basic component of the various quenching solutions.

What I claim is:

1. The method of quenching quench-hardenab'le steel in an austenitiic condition from above the austenite transformation range to below the Ms temperature to produce hardening, comprising immering it in a solution of a soluble gum in water.

2. The method .of quenching :quench-hardenable steel in an austeniticcondition from above the austenite transformation range to below the Ms temperature to produce hardening, comprising immersing it in a solution of from 0.1 percent to not substantially higher than 1.0 percent of a solublegumin water.

3. The method of quenching quench-hardenab'le steel in an austen'itic condition from above the austenite transformation range to below the Ms temperature to produce hardening, comprising immersing the :steel in a water solution in which is dissolved a small percentage of a gum selected from the group consisting of methyl cellulose, carboxy methyl cellulose, hydroxy ethyl cellulose, and carboxy methyl-hydroxyzethyl cellulose.

4. The method of claim 3 wherein the solution consists of 0.1 to 1.0 percent of the gum and substantially the rest Of the solution is water.

'5. The method of claim 4 wherein the solution include-s a mall percentage of a Wetting agent.

6. The method of controlling internal structure in a composition of metals and metalloids having a structure transformation range, comprising heating the composition to the temperature at the upper end of said range where the composition goes into solid solution, then cooling said material through said transformation range in a 'water solution "in which is dissolved a small percentage of a guru selected from the group consisting of methyl cellulose, car boxy methyl cellulose, hyd roxy ethyl cellulose, and carboxy methyl-hydroxyethyl cellulose.

7. The method of claim 3 including the step of agitating said solution WhllB the steel is immersed therein to prevent the accumulation of steam bubbles on said material in said solution.

8. The method of controlling internal structure in pearlitic malleable iron having a structure transformation range, comprising heating the iron to the temperature at the upper end of said range Where the composition goes into solid solution, then cooling said iron through said transformation range in a Water solution of a soluble gum.

9. The method of controlling internal structure in pearlitic malleable inon having a structure transformation range, comprising heating the iron to the temperature at the upper end of said range where the composition goes into solid solution, then cooling said iron through said transformation range in a Water solution in which is dissolved a small percentage of a gum selected from the group consisting of methyl cellulose, carboxy methyl cellulose, hydroxy ethyl cellulose and carboxy methylhydroxy ethyl cellulose.

References Cited in the file of this patent Industrial and Engineering Chemistry, October 1945, pages 943-947. 

1. THE METHOD OF QUENCHING QUENCH-HARDENABLE STEEL IN AN AUSTENITIC CONDITION FROM ABOVE THE AUSTENITE TRANSFORMATION RANGE TO BELOW THE MS TEMPERATURE TO PRODUCE HARDENING, COMPRISING IMMERING IT IN A SOLUTION OF A SOLUBLE GUM IN WATER. 